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\NNUAL WHITE SWEET CLOVER AND 
STRAINS OF THE RIENNIAL FORM 



A. J. PIETERS 

Agronomist in Charge of Clover Investigations 
and 

L. W. KEPHART 

Scientific Assistant 




UNITED STATES DEPARTMENT OF AGRICULTURE 
DEPARTMENT CIRCULAR 169 



Contribution from the Bureau of Plant Industry 

(Office of Forage-Crop Investigations) 

WM. A. TAYLOR, Chief 



Washington. D. C. Issued April, 1921 



WASHINQTON : GOVERNMENT PRINTINQ OFFICE : 1921 



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ANNUAL WHITE SWEET CLOVER AND STRAINS 
OF THE BIENNIAL FORM. 



CONTENTS. 



Page. 

Annual white sweet clover 3 

Wild annual white sweet clover 6 

Can the annual plants he distin- 
guished from those of the hiennial 

form? 7 

Can the seed of the annual he dis- 
tinguished from that of the bien- 
nial form? 8 

Variations in annual white sweet 

clover 1(1 



Page. 
Annual blossoming biennial forms. _ 12 
Uses for annual white sweet clover_ 12 
Value of differeiit varieties of bien- 
nial white sweet clover 17 

Strains of biennial white sweet 

clover 18 

Grundy County sweet clover 19 

Arctic sweet clover 20 

Summary 21 



ANNUAL WHITE SWEET CLOVER. 

In the spring of 191G Prof. H. D. Hiiorhes, of the Iowa Agricul- 
tural Experiment Station, discovered that certain white sweet-clover 
plants growing in the greenhouse Avere blooming the first year. 
Later in the season Mr. H. S. Coe, of the United States Department 
of Agriculture, found similar plants at both Redfield, S, Dak., and 
Fargo, N. Dak., in the regional strain plats sown with Alabama 
seed. The other plats showed no annuals. Prof. Hughes distributed 
small quantities of seed to agricultural experiment station workers 
and to some private individuals, some of whom have propagated the 
seed and sold it at high prices. During the season of 1920 one firm 
contracted for 20 bushels of seed at $300 a bushel. 

Naturally, much interest was aroused by statements of the rapid 
growth of this variety. During the past two years many articles 
have appeared in the agricultural press commending the crop very 
highly. It has even been predicted that it would revolutionize the 
agriculture of the corn belt. The nature of this new variety is cer- 
tainly such as to indicate that it may have important possibilities. 
Whether all of these hopes will be realized remains to be seen. 

Though Prof. Hughes was the first to call the attention of agrono- 
mists to the variety, it had probably been observed by the late Prof. 
S. M, Tracy as early as 1898. In "Forage Plants and Forage Re- 
sources of the Gulf States," he says, writing of MeJilotus alba^ " a 
few plants will produce seed the first year and a few will live three 
years." 

It is, however, uncertain whether Prof. Tracy referred to genuine 
annual plants or to the biennial form which sometimes blooms 

3 



4 Department Circular 169, IL S. Dept. of Agriculture. 

the first year. In 1917, when Mr. Tracy's- attention was called to 
the discovery of the annual, he insisted that the words quoted above 
referred to the annual variety. Some time before 191G Dr. W. B. 
Gernert, then of the Illinois Agricultural Experiment Station, dis- 
covered the annual variety and propagated it to some extent. In a 
letter dated April 15, 1918, Prof. C. G. Hopkins said : " The Illinois 
station has been growing the annual white sweet clover for several 
years. In 1917 we harvested about 5 bushels of seed, and we now 
have about 10 acres of this crop growing." In 1914 the Illinois 
Agricultural Experiment Station had photographs and notes on this 
variety together with records of the comparative weights of the 




Fig. 1. — Roots of white sweet clover : Left, wild growth of the biennial form ; center, 
biennial form from a cultivated row ; right, annual form from a cultivated row. 

annual and the biennial forms. Dr. Gernert has kindly supplied 
from these records the data show^n in Table I. 

Table T. — Growth data of the annual and Mcnnial forms of ichitc stircct clover 
at the Illinois Auricultural Exiterinient station. 



Speciflcation. 


Annual 
form. 


Biennial 
form. 


Height 




centimeters. . 


157 

88. C2 
8.93 


119 


Air-dry weight: 

Top 




grams.. 


117.54 


Root 




do 


33.69 







Annual White Sweet Clover. 



The annual variety was also observed in Arkansas in 1916. Tlie 
writers are indebted to Dr. Gernert for a reference to Gleanings in 
Bee Culture, Decem- 
ber 15, 1916, where 
this observation is 
recorded. 

There is no record 
at the Iowa Agricul- 
t u r a 1 Experiment 
Station showinc; 
where the original 
seed out of which the 
annual variety was 
selected was grown. 
The Illinois strain 
was selected from a 
lot of seed purchased 
in Falmouth, Ky., 
and reported to have 
been grown in Ala- 
bama. The plants 
found at Redfield and 
Fargo were in plats 
sown with seed from 
Alabama. 

Mr. Coe described 
the annual variety, 
giving it the name of 
MelUotus alha x'av. 
annua.^ and called at- 
tention to the botan- 
ical characters in 
w h i c h it differed 
from the biennial 
plant. 

The annual has a 
smaller, more woody 
root than the bien- 
nial form, and crown 
or resting buds are 
not formed. (Fig. 
1.) The stems, 
branches, leaves, 
flowers, pods, and 
seeds are indistin- 
guishable from those of the biennial form, but during the season of seed- 
ing the plant grows more rapidly, blossoms, fruits, and dies. (Fig. 2.) 




Fig. 2. — A group of annual white s\v<'i>t-cIover plants 4 
months after seeding. The plants vary in size and 
development. 



6 Department Circular 169, U. S. Dept. of Agriculture. 
WILD ANNUAL WHITE SWEET CLOVER. 

The seed of annual white sweet clover that has been sold so far and 
most of that on the market during 1920 was produced from the Iowa 
strain. During the summer of 1920, however, interest in this variety 
was aroused in Alabama, in Hale and Perry Counties, where it occurs 
with the biennial form, and some seed from that source will doubt- 
less be on the market later. 

It is not possible at present to place any limit on the range in which 
annual white sweet clover may be growing wild. It has been found 
chiefly in Alabama, but is also present in natural wild growths of 
Melilotus alha about Washington, D. C. In waste places near the 
Potomac River in Virginia, just outside of Washington, there are 
considerable areas used as dumping places for mortar and building 
refuse. These dumping grounds are covered every summer with a 
dense growth of sweet clover, and a few annual plants are to be 
found. Their number would equal but a small fraction of 1 per cent 
of the total plant population, however. 

How, when, or where the annual variety originated is not known. 
Statements have appeared to the effect that the ver}^ hill slope in 
an Alabama county on which this variety originated had been located. 
It seems doubtful whether such claims can be taken seriously, with 
the evidence at hand. As already stated, it is probable that this 
variety was observed in the South as early as 1898. The fact that 
annual specimens were found about Washington after careful search 
over considerable areas of wild growth suggests that the tendency to 
sport in this way may be inherent in Blelilotus alha. Conditions in 
Alabama may have been especially favorable for the increase of this 
variety, thus giving it greater prominence there. 

So far a very superficial examination has sliown that the plants 
occur in sufficient abundance for seed gathering only in the counties 
in Alabama mentioned. The harvesting of seed appears to be done 
mainly about Uniontown and Newbern. Throughout this section the 
annual plants are found either mixed with the biennial form or in 
more or less pure growths in fields or in patches. Since the two 
varieties occur in more or less mixed stands, the purity of the seed 
gathered depends on the ability of the person harvesting to distin- 
guish the two forms. 

In the latitude of Washington, D. C, the annual plants begin to 
bloom at about the time the biennials are in full bloom. Both forms 
have, however, a long flowering period, and during most of the time 
from the middle of July to September both annuals and biennials 
may be found bearing flowers and young or mature pods. 



Annual White Sweet Clover. 7 

CAN THE ANNUAL PLANTS BE DISTINGUISHED FROM THOSE OF 
THE BIENNIAL FORM? 



The annual and the biennial forms, of course, can be readily dis- 
tinguished by the roots, as already explained. When harvestino; seed, 




Fig. 3. — Typical biennial white sweet-clover plant during the second season. Note the 
dead stubble of the previous year's growth (a) and the many branches from the 
crown buds. 

however, one can not examine all the roots. When the growth of the 
biennial form in bloom is typical, it has also a distinctive habit. The 
slender stem of the first season's growth is killed and is represented 



8 Department Circular 169, U. S. Dept. of Agriculture. 

by a stub ot dead tissue. Around this stub and coming from the 
crown are two to several strong branches, the growths from the rest- 
ing buds (fig. 3-) . Such branches never occur in the annual form. 

The habit of growth of the biennial is not always typical, however. 
In every natural stand, .especially if it is thick, there are a number of 
plants with apparently one central stem only. An examination of the 
root will show that this stem is not truly central, but has come from a 
lateral resting bud. By the suppression of the other buds and the 
total disappearance of a central stem, the one branch appears to be a 
central stem (fig. 4). How large a percentage of such plants may 




Fiu. 4. — Stems and roots of biennial wtiite sweet clover. The four stems at the left 
may readily be mistaken for those of annuals. Note the old stubbles on several 
plants. 

occur in a natural stand of biennial sweet clover is not known, but it 
can readily be seen that where a mixed growth of annuals and bi- 
ennials occurs such plants are easily mistaken for annuals. Great 
care will be necessary, therefore, when harvesting seed from such a 
stand. 

CAN THE SEED OF THE ANNUAL BE DISTINGUISHED FROM THAT 
OF THE BIENNIAL FORM? 



The statement has been made that the seed of the annual white 
sweet clover can be distinguished from that of the biennial form, 



Annual White Sweet Clover. 9 

but the Seed Laboratory of the United States Department of Agri- 
culture has been unable to confirm this statement. 

The writers secured from a reliable correspondent in Wilcox 
County, Ala., a large number of samples taken from both annual and 
biennial plants of white sweet clover. Samples were also obtained 
by an agent of the United States Department of Agriculture from 
lots of seed harvested in Alabama as that of the annual variety. 
Further samples were taken from plants grown from the department 
strain of the annual form. All of these, together with authentic 
biennial seeds and commercial biennial seeds, were submitted to Mr. 
F. H. Hillman, of the Seed Laboratory, with the request that a study 
be made to determine whether any constant and reliable difference 
exists by which seed of the annual may be certainly distinguished 
from that of the biennial form. His report is given herewith. 

The 62 samples of seetl of sweet clover, part from annual and part from 
biennial plants, were received with your letter of August 31. 

These samples are our Nos. 724077 to 72413S, inclusive. I have examined 
them with a view to finding means by which seed from annual plants may be 
distinguished from that from biennial plants. 

Both pods and seeds have been carefully examined under a low-power com- 
pound microscope, and I fail to find any external characteristics by which pods 
or seeds from annual plants may be distinguished from those from biennial 
plants. 

Pods from different lots sometimes differ considerably in appearance, ap- 
parently due to conditions prior to harvesting, but this is evident alike in pods 
from both annual and biennial plants. Likewise, differences in the seed are 
observable, but they appear in seed from both types of plants. 

Later, seed of the Iowa strain of the crop of 1920 was secured 
from the two largest producers. This seed could not be distinguished 
from that of the biennial form. 

It appears, therefore, that no one can tell whether any particular 
lot of seed is that of the annual or the biennial form. This is of great 
importance, in view of the present interest in the variety and the 
high prices being paid for seed. To the possibility of honest error, 
especially in the case of wild seed, must be added the temptation that 
always exists in such cases for dishonest dealers to sell seed of one 
variety for that of the other or to mix the seed. Buyers are cautioned 
to use care and whenever possible to demand the pedigree of the seed 
offered. The strain developed by the United States Department of 
Agriculture has not been generally distributed, and samples of the 
Illinois strain are reported to have been sent only to several persons 
in Edgar County, 111., in the spring of 1919 and again in 1920. All 
commercial lots offered during the season of 1920-21 as specially 
grown should therefore trace back to the Iowa strain. 

34985°— 21 2 



10 Department Circular 169, U. S. Dept. of Agriculture. 
VARIATIONS IN ANNUAL WHITE SWEET CLOVER. 

The biennial white sweet clover is extremely variable, varying in 
size, habit, productiveness, and date of maturity. Many of the varia- 
tions are certainly due to local conditions, such as the presence of 
an abundance of lime or the absence of lime. Many variations are, 
however, undoubtedly inheritable. 

The annual white sweet clover is also extremely variable. During 
the summer of 1920 the United States Department of Agriculture 




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Fig. 5. — Relative heights in inches on July 16 of 65 annual white sweet-clover plants 
grown consecutively in row 10001-C by the United States Department of Agriculture. 

sowed several rod rows to various lots of annual white sweet clover, 
the seed being selected from the department strain, from the Iowa 
strain, and from the Illinois strain. So far as is loiown, none of 
these selections were from self-fertilized individual plant's. The 
plants of each row were thinned to stand from 6 to 8 inches apart in 
the row. All the plants of a lot thus had practically identical soil 
conditions. The diagram (fig. 5) represents the variations in height 
of 65 consecutive plants in the row of the department's selection 
No. 10001-C. Seed was sown on April 10, 1920, and measurements 
"Were made on July 16, at which time most of the plants were coming 



Annual White Sweet Clover. 



11 



into bloom. The plants in the other rows showed similar variations. 
In date of blossoming there was also considerable variation. The 
first observation was made on July 14, when fully opened racemes 
were found on many plants. These were all removed. Later observa- 
tions showed that' different plants came into flower at various times 
and as late as August 10. 

The diagrams (fig. 6) show the relative percentage of all the 
plants in a lot that came into flower at the dates specified. 

Much variation was also noted in branching habit, leafiness, and 
seed-producing capacity.^ 




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Pig. 6. — Diagrams showing the percentage of plants of annual white sweet clover which 
blossomed at different dates. 

None of the annual white sweet-clover strains so far tested by the 
United States Department of Agriculture are wholly free from some 
biennial blood. During the past summer, samples of five lots were 
planted at the Arlington Experimental Farm, near Washington, 
D. C, and also in cooperation with the Tennessee and Kansas Agri- 
cultural Experiment Stations at Knoxville, Tenn., and Manhattan, 



^ While this circular was in press, information was received from Mr. Willis Crites, a 
breeder of annual white sweet clover, tliat plants gi'own in the greenhouse from wild 
Alabama seed of the annual form are much earlier than those from the Iowa strain. 
On February 4, plants from the Alabama strain were 30 inches high, while those from 
the Iowa strain were 9.0 inches high. Alabama seed planted for increase in Texas is 
also said to have produced plants materially earlier in maturity than those from the 
Iowa strain. As has already been pointed out, the annual fonns of white sweet clover 
are extremely variable in date of maturity, and Mr. Crites suggests that since in Alabama 
the earlier strains ripen before the seed crop of the biennial forms is harvested seed 
of the later strains only will occur as mixtures in the biennial seed. The Illinois annual 
strain and also that of the United States Department of Agriculture are known to have 
been selected from seed of the commercial biennial form grown in Alabama, and this was 
probably also the case with the Iowa strain. 



12 Department Circular 169, U. S. Dept. of Agriculture. 



Kans. The percentage of biennial plants resulting in each case is 
shown in Table II. 

Table II. — Percentage of biennial plants grown in 1920 in Virginia, Tennessee, 
and Kansas from seed of annual white sweet clot^er. 



United States Department of Agriculture numbers. 



10001-A 

10001-B 

10001-C 

10030 (Iowa) 

10042 (Illinois)... 
Tennessee Early. 



Arlington, 
Va. 



4.3 
5.9 
3.0 
3.5 




KnoxviUe, 
Tenn. 



3.95 
4.70 
2.04 
8.00 
1.17 




Manhattan, 
Kans. 



Seed lots numbered 10001-A, 10001-B, and 10001-C were various 
selections made by the United States Department of Agriculture and 
were, respectively, the second, third, and fourth generations from 
the original plants found in the Alabama plat at Redfield, S. Dak. 
The Tennessee Early was a selection made by the Tennessee Agri- 
cultural Experiment Station from seed received from Prof. H. D. 
Hughes. 

ANNUAL BLOSSOMING BIENNIAL FORMS. 

The biennial sweet clover sometimes blossoms in the fall of its 
first season. This occurs in Alabama and Mississippi, and it has been 
found more or less frequently in both wild and cultivated stands 
about Washington, D. C. 

On the dumping grounds near Washington previously referred to, 
some 30 biennial plants were found in bloom on an area of perhaps 
5 acres. These plants had normal resting buds and large roots. On 
a few ripe seeds were found, but for the most part the flowers opened 
too late to set seed before frost (fig. 7). In a field some distance from 
Washington, near Gaithersburg, Md., that had been sown to white 
sweet clover in the spring of 1920 a large number of such flowering 
plants were found. Possibly this habit may not be uncommon in 
the biennial form, but so far as known there are no recorded observa- 
tions on this point. 

USES FOR ANNUAL WHITE SWEET CLOVER. 

It should be understood that whatever is said about the probable 
uses and value of annual white sweet clover is based mainly on the 
characteristics of the plant and general knowledge of agriculture 
rather than upon results obtained in field experiments with the 
new crop. 

Annual white sweet clover makes a rapid growth after becoming 
established, blooms early, and ripens seed about August when seeded 



Annual White Sweet Clover, 



13 



early, and dies after seeding. The root system is slender and the 
roots relatively woody, compared with the roots of the biennial form. 

Many farmers, agricultural writers, and some experiment-station 
workers are very enthusiastic about the possibilities of this variety. 
One eastern agricultural paper said " we believe the discovery of this 
plant is to work a revolution in the cultivation of our northern soil." 
So far as the United 
States Department 
of Agriculture is 
aware, no compara- 
tive trials have been 
made with annual 
white sweet clover. 
This is quite natural, 
as there has not been 
seed enough for ex- 
tensive trials. The 
supply available in 
the fall of 1920 is 
probably not more 
than 150 or 200 bush- 
els, all held at figures 
too high to warrant 
its use in growing a 
hay or a green-ma- 
nure crop. Some re 
ports regarding this 
variety have ap- 
peared, however, in 
the agricultural 
press, and the writers 
have received some 
data by correspond- 
ence. These reports 
so far as they appear 
to be based on actual 
observations are con- 
sidered in what is 
said below. 

Probably the greatest use of annual white sweet clover for hay will 
be as an emergency crop. When a stand of clover has been winter- 
killed or when for any reason a farmer finds that his hay suppl}^ 
for the season will be short, this variety can be seeded on any vacant 
piece of land, provided lime and the proper bacteria are present, 
with every expectation of a fair to good hay crop. Prof. J. F. Cox, 
of the Michigan Agricultural College, wrote that in early July the 




Fig. 7. — A biennial white sweet-clover plant which blos- 
somed in the autumn of its first season. Note the large 
crown buds below and the two flowering branches. 



14 Department Circular 169, U. S. Dept. of Agriculture. 

stand " would undoubtedly have given a yield of hay comparable to 
a heavy cutting of alfalfa or clover; " also that at the "Upper Pen- 
insula substation at Chatham an excellent forage growth was se- 
cured." 

Where rainfall is sufficient annual white sweet clover may be 
seeded even after wheat harvest. 

It is possible that this annual variety may help in controlling the 
Hessian fly. Entomologists have shown that for the control of this 
pest the wheat stubble should be plowed immediately after harvest. 
The presence of red clover in the stubble usually makes this unde- 
sirable, however. With the annual white sweet clover it may be 
possible to plow the wheat stubble and still make a hay crop the 
same season. This can also be done with soy beans, but at consider- 
ably more expense than is required to grow a crop of sweet clover. 
The rapid growth of annual white sweet clover will probably enable 
it to keep ahead of the weeds. 

Those most enthusiastic about this variety expect great things 
from it as a soil builder and source of nitrogen. An Illinois man, 
one of the leading county agents in the United States, whose opinion 
must be regarded with respect, writes as follows : 

I consider the place that this clover will play in our agriculture, perhaps, 
first of all the clovers . . . Instead of 4-year rotations in the corn belt, 
consisting of corn, corn, oats, and clover, we would have a 2-year rotation of 
corn and small grain seeded to sweet clover ; in other words, on 160 acres of land 
80 acres would be in corn and 80 acres in small grain seeded to sweet clover. 
This 80 acres seeded to sweet clover would be fall plowed for next year's corn 
crop. You eliminate the danger of winterkilling of red clover, and there would 
be turned under a legume on SO acres per year instead of 40 acres per year. 
This, I believe, will solve the corn-belt nitrogen problem, especially on grain 
farms. 

In considering the possible value of a green-manure crop where 
there is as yet no actual performance, the characteristics of the crop 
and general principles must guide in forming conclusions. A good 
green-manure plant should be an efficient nitrogen gatherer and pro- 
duce a large mass of material for turning under. It must fit into 
farm practice, unless, indeed, the crop becomes so important that 
farm practice, especially in rotations, is altered so as to permit its use. 
The best time to turn under a green-manure crop so as to get the 
maximum benefit, the desirability of spring or fall plowing, and the 
need or value of a winter cover crop must also be taken into account. 
No analyses have yet been published covering the quantities of or- 
ganic matter and nitrogen in a crop of annual white sweet clover. 
This clover is known to make a good growth the first season, and ex- 
perience in Iowa and Michigan has shown that it may be seeded on 
winter wheat or with oats and will make a fair to good growth after 



Annual White Sweet Clover. 15 

the grain is harvested. Agricultural practice varies under different 
conditions of soil and climate, so that what may be good practice in 
one section may be bad in another. Further data in regard to the 
relation of annual white sweet clover to these various factors will 
doubtless develop in the next few years. It is particularly desirable 
that studies be made of the effect on nitrate production and conserva- 
tion of turning under a dry, ripe crop of annual white sweet clover 
in the fall. Whiting and Schoonover, at the University of Illinois 
Agricultural Experiment Station, have shown that there was con- 
siderable nitrate formation in the fall, continuing to the end of No- 
vember or later; also that nitrates might be lost in early spring 
when there was no crop on the ground. These facts may have a 
bearing on the total nitrates that may be made available for a com 
crop by turning under a crop of annual white sweet clover the pre- 
ceding fall. 

In north-central Indiana hogs are pastured on clover in the spring, 
before the field is plowed for corn. With annual white sweet clover 
this practice will be impossible. It must be borne in mind that the 
annual form can not be used for a hay crop or a seed crop and for a 
soil improver at the same time. When a hay crop is cut the growth 
is mostly at an end. It has been abundantly demonstrated that 
legumes take only a part of their nitrogen from the air. The best 
of them leave little, if any, increase of nitrogen in the soil when only 
roots and stubble are turned under. With the relatively slender 
root system of annual white sweet clover it may be doubted whether 
the soil will be improved unless the entire crop is turned under. 

In certain grain-growing sections red clover is seeded in wheat, 
to be turned under for the next wheat crop. Annual white sweet 
clover may prove to be well fitted for such rotations. It will almost 
certainly make more growth during the season than either red clover 
or the biennial sweet clover and will have the additional advantage 
over the latter that it will be dead when turned under in the fall 
and will not volunteer in the grain the next season. 

As an orchard cover crop the annual white sweet clover may have 
an important place. In Nebraska a cover crop that will die in the 
fall is wanted. This clover would be such a crop. In many or- 
chards on the Atlantic coast also a legume that will die in the fall, 
leaving a good growth of dead stalks to hold the snow, may be 
useful. A correspondent in Ohio believes that a mixture of annual 
white sweet clover and hairy vetch seeded in orchards and vineyards 
in July may prove valuable. 

Perhaps the most important place for annual white sweet clover as 
a soil improver will be as a catch crop, to be seeded after early po- 
tatoes, grain, or any crop coming off by early August. Seeded at 
that time this will make a considerable growth before frost. At 



16 Department Circular 169, U. S. Dept. of Agriculture. 



the Arlington Experimental Farm, Va., the annual white sweet 
clover was seeded on August 11. On September 20 the plants were 
2 to 6 inches high, and on October 16 they averaged knee-high. It 



Afl 



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Fig. 8. — Plants of annual white sweet clover on October 16,. 65 days after seeding. At 
the left, three plants from seed sown in an open field ; at the right, six plants from 
a seeding in an adjacent conifleld. 

should be noted, however, that a planting in corn made on the same 
date failed to make a satisfactory growth (fig. 8). 

Studies in green manuring have established the fact that for the 
greatest benefit, such a manure should be turned under so that the 



Annual White Sweet Clover. 17 

maximum decay will take place during the height of the growing sea- 
son. This will probably never be possible with annual white sweet 
clover. Illinois farmers have found, however, that considerable soil 
improvement, as measured by crop returns, takes place when the crop 
residues from a sweet-clover seed crop are turned under in the fall. 
The annual variety may act similarly, but there will not be as large 
a quantity of dry matter in a single season's growth of the annual 
as in a seed stand of the biennial form. 

The opinion of many men of good judgment is that the new variety 
will prove valuable. It has its limitations, however, and these should 
be frankly recognized. Unless this is done, there is certain to be con- 
siderable disappointment, and a reaction may set in against it. For 
a crop to be valuable for green manure, especially as a catch crop, it 
is essential that the seed be cheap and always readily obtainable. 
The annual white sweet clover can not be expected to make both a 
hay and a seed crop, as red clover and biennial sweet clover do. The 
seed will have to be grown as a special crop. While the high prices 
at present prevailing continue, plenty of seed will be produced, but 
eventually the industry, if it is to live, will have to be based on the 
value of this variety as a forage or soil-improving crop. Unless a 
regular demand for the seed develops at prices at which farmers can 
afford to use it liberally for the purposes specified, the variety will 
fail to make a place for itself. 

It has seemed well, therefore, to offer the suggestions contained in 
this circular with the hope that as soon as more seed is available 
many trials of this variety will be made. In this way its proper 
place in our aginculture will soon be determined. 

VALUE OF DIFFERENT VARIETIES OF BIENNIAL WHITE SWEET 

CLOVER. 

During the past 10 years there has been a rapid advance in interest 
in sweet clover, especiallj^ white sweet clover. The crop has been 
introduced into many sections in which it was not before cultivated, 
so that to-day it is highly regarded from Alabama to North Dakota 
and from New York to Montana. The seed is now produced in 
many States. In the process of seed production a number of distinct 
strains or types have appeared, some of them markedly different in 
size, vigor, and time of maturity from the common wild sweet clover. 
Sufficient time has not elapsed to fix the characters of all the various 
strains, but a few special strains have appeared, and it seems prob- 
able that as this crop is kept under more careful observation, other 
more or less distinct strains will be found. AVhether these strains 
will be of value can be determined only by repeated trials. We 
know, in general, that strains of cultivated plants that may prove 



18 Department Circular 169, U. S. Dept. of Agriculture. 

valuable for one purpose may be useless for another and that some 
may be better able than others to withstand drought, alkali, and other 
unfavorable conditions. We may expect, therefore, that this will be 
the case with sweet clover. The attention of growers of sweet clover 
especially is directed to this matter, in order that further observa- 
tions may be made and recorded. 

Attention should be called at the outset to the fact that the value 
of a variety depends on the use to which the crop is to be put. Sweet 
clover is used for forage, pasture, and soil-improving purposes. The 
seed is used only for sowing. True, at this time seed growing is of 
great importance, because the rapidly increasing use of sweet clover 
makes heavy demands on the seed crop. A strain, however, that pro- 
duces a large quantity of seed and but little forage or pasture or 
which has no special value as a green-manure crop would have to be 
classed as an inferior variety. On the other hand, a strain might 
appear that, while of superior forage or pasture value, was so poor a 
seed producer as to make it unprofitable. The ability to produce seed 
plentifully is of distinct value, provided the resulting crop is as good 
as or better than that produced by the seed of other strains. 

STRAINS OF BIENNIAL WHITE SWEET CLOVER. 

At the Agricultural Experiment Station of the University of 
Illinois a study of individual strains of sweet clover was commenced 
in 1913, but no results have yet been published. In 1916 seed har- 
vested in the States of Alabama, Mississippi, Kentucky, Kansas, 
North Dakota, Montana, and Wyoming was sown at the field station 
of the United States Department of Agriculture at Redfield, S. Dak., 
and at Fargo, N. Daik., the latter in cooperation with the North 
Dakota Agricultural Experiment Station. Further sowings were 
made each year up to 1919, when the final sowings in this series were 
made at Fargo. Besides the lots mentioned, seed from Oklahoma 
and South Dakota and two lots from Illinois were included in the 
test in 1917. Little is known of the histor}^ of these regional strains. 

The seed from Alabama, Mississippi, and Kentucky probably had a 
long local history, while that from the northern stations can certainly 
not have been grown there for many years. No final conclusions can 
yet be drawn from these tests ; so far, the results are suggestive only. 
Each year notes were made on the extent of winterkilling, and the 
weights of hay were taken. The results with seed of Alabama and 
Mississippi origin have quite consistently been less satisfactory than 
those with northern and western grown seed. On the other hand, 
Oklahoma seed has given results equal to the best, and results with 
Wyoming seed have been unsatisfactory. It is doubtful whether the 
term " regional strains " has any but a vague general significance at 



/ 

Annual White Sweet Clover. 19 

present. With the exception of the seed from Illinois, these regional 
strains did not differ from one another in size, earliness, or other char- 
acters, except possibly in winter hardiness, although the evidence is 
inconclusive. 

Only two distinct varieties were found, both from Illinois and both 
earlier than the common white sweet clover. One of these. No. 1619, 
has a partly decumbent habit and appears to be somewhat inferior, 
both as a hay and as a seed producer. 

GRUNDY COUNTY SWEET CLOVER. 

The attention of the United States Department of Agriculture has 
lately been called to a special strain from Illinois, developed in 
Grimdy County. Nothing is known of its origin except that the 
seed was first procured about four years ago from a local dealer. 
Like the other sweet clovers from Illinois, the Grundy County strain 
is earlier and not as tall as the ordinary biennial sweet clover. It has 
an erect habit of growth, most of the plants consisting of a single 
upright stem which does not branch freely until about 10 or 12 inches 
from the gi'ound. The plants seldom grow more than 4 feet high, 
and the main stems are scarcely larger than a lead pencil. In leafiness 
the plants compare favorably with ordinary sweet clover. 

The principal use of a sweet clover of the Grundy County type 
is for the production of seed. The plants being small are easily har- 
vested with a grain binder, and the seed is readily thrashed with a 
clover huller. Furthermore, the plants ripen from ten days to two 
weeks earlier than ordinary sweet clover, which is a very practical 
advantage, since it brings the seed harvest before the winter-wheat 
harvest instead of right in the midst of it, and the sweet clover also 
ripens ahead of the weeds. The seed yield from the Grundy County 
strain has been about 10 bushels per acre, which is practically the same 
as that obtained from ordinary sweet clover. The ordinary plants are 
twice as large as the Grundy County plants and have more blossoms, 
but the seed yield is no gi'eater, because the ordinary clover ripens un- 
evenly and shatters badly, whereas the crop of the Grundy County 
type ripens all at once and all the seed can be saved. 

There is little information as to the usefulness of the Grundy 
County type for hay and pasturage, as the demand for seed has 
been so great that practically all of the crop has been saved for that 
purpose. It is evident, however, that a sweet clover of this class is 
a specialized rather than a dual-purpose type and approaches the 
type previously referred to as excellent for seed production but of 
less value for forage. One of the main uses for sweet clover is 
as summer pasturage, to take the place of bluegrass and other 
pasturage which dries up by the middle of July. A sweet clover 



20 Department Circular 169, U. S. Dept. of Agriculture. 

which ripens by July 15 would therefore not be as desirable as one 
which stays green until August. In addition, the quantity of pas- 
turage would probably be less, owing to the smaller size of the plants. 

While as a hay producer this type can hardly equal the larger ordi- 
nary sweet clover in quantity, Grundy County farmers who have 
made hay from this stfain are very enthusiastic about it both for its 
superior quality and the fact that it is more easily made into good 
hay than the coarser ordinary sweet clover. The finer stems, even 
the straw, make a good feed which is relished by live stock. 

The exact opposite of the Grundy County type of sweet clover was 
found in northwestern Ohio during the summer of 1920. In at 
least three different localities a sweet clover was found which grew 
10 or 12 feet high and was 7 to 10 days later in blossoming than 
ordinary sweet clover. The soil was rich virgin bottom land, but 
this does not account entirely for the unusual size or the delayed 
maturity of these plants. These mammoth plants produced a large 
quantity of seed, but were so unwieldy that the harv^esting of the 
seed was not profitable. Because of their coarse, woody nature the 
plants were not suitable for hay, but they provided good late 
pasturage and were probably of superior value for enriching the soil. 

A type of sweet clover resembling the Grundy County type has 
also been oted in western Ohio. These plants are uniformly smaller 
and earlier than ordinary sweet clover and are rather notable for 
their leafiness. Neither' of the Ohio types has yet been developed 
commercially. 

ARCTIC SWEET CLOVER. 

A variety introduced under the name of Arctic sweet clover by the 
University of Saskatchewan appears to have been very successful in 
the Provinces of western Canada. It is said by Prof. Manley 
Champlin to have been developed by Profs. Bracken and Kirk from 
a sample received by them from Prof. N. E. Hansen, of South 
Dakota. It is presumably of Siberian origin and is said to be hardy, 
early, and a good seed producer. It does not produce as much forage 
as the common sort, but its hardiness, earliness, and good seed pro- 
duction appear to make it desirable for the extreme north. 

Sweet clover should be a particularly easy plant with which to 
carry on selection work for the development of new varieties and 
types. The strains which have been selected already were acquired 
largely by accident, very little effort having been spent in a sys- 
tematic search for types. Because of the widespread interest in this 
crop and the many uses to which it is adapted it would seem well 
worth while for farmers and official plant breeders to devote some 
time to the development of new and useful strains. 



Annual White Sweet Clover. 21 

SUMMARY. 

The annual form of white sweet clover has been known to be in 
existence for an indefinite time. Its possibilities as a crop plant 
were, however, first called to the attention of agronomists generally 
in 1916 by Prof. H. D. Hughes, of the Iowa Agricultural Experi- 
ment Station. 

This variety differs from the biennial form in its more rapid 
growth and maturity. Crown buds are not developed, but the plant 
dies after j)roducing seed. 

When two or more crown buds develop on a biennial the habit of 
the plant when in seed is distinct from that of a seed-bearing annual, 
but when only one crown bud develops the biennial and the annual 
seed-bearing plants can not be distinguished with certainty. 

The seeds of the annual are like those of the biennial form ; they 
can not be distinguished. Seed is still scarce, some having been 
grown from the Iowa strain and some harvested from wild plants in 
Alabama. 

Both the biennial and the annual white sweet clovers are quite 
variable as to height, leafiness, and date of maturity. The biennial 
form occasionally blossoms in the autumn of the first season. 

There is at present no definite knowledge as to the value of annual 
white sweet clover, but agriculturists of experience consider that it 
will prove especially useful as a soil improver. 

There are some well-defined strains of biennial white sweet clover. 
It is possible that others may be developed and found available for 
certain situations or uses. 



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